• Atmosphere
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• v.23 no.1
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• pp.13-21
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• 2013

In this study, the effects of atmospheric stability and surface temperature on the microscale local airflow are investigated in a hydrological suburban area using a computational fluid dynamics (CFD) model. The model domain includes the river and industrial complex for analyzing the effect of water system and topography on local airflow. The surface boundary condition is constructed using a geographic information system (GIS) data in order to more accurately build topography and buildings. In the control experiment, it is shown that the topography and buildings mainly determine the microscale airflow (wind speed and wind direction). The sensitivity experiments of atmospheric stability (neutral, stable, and unstable conditions) represent the slight changes in wind speed with the increase in vertical temperature gradient. The differential heating of ground and water surfaces influences on the local meteorological factors such as air temperature, heat flow, and airflow. These results consequentially suggest that the meteorological impact assessment is accompanied by the changes of background land and atmospheric conditions. It is also demonstrated that the numerical experiments with very high spatial resolution can be useful for understanding microscale local meteorology.

• Ocean Science Journal
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• v.43 no.4
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• pp.165-173
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• 2008

In this article, we describe a simple yet effective method for insertion of observational datasets in a mesoscale atmospheric model used in one-dimensional configuration through Nudging. To demonstrate the effectiveness of this technique, vertical profiles of meteorological parameters obtained from GLASS Sonde launches from a tiny island of Kaashidhoo in the Republic of Maldives are injected in a mesoscale atmospheric model - Advanced Regional Prediction System (ARPS), and model simulated parameters are compared with the available observational datasets. Analysis of one-time nudging in the model simulations over Kaashidhoo show that incorporation of this technique reasonably improves the model simulations within a time domain of +6 to +12 Hrs, while its impact on +18 Hrs simulations and beyond becomes literally null.

• Journal of the Korean institute of surface engineering
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• v.50 no.6
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• pp.447-454
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• 2017

Al1050 and Al7075 alloy specimens were exposed to atmospheric conditions for maximum 12 months and analyzed by Transmission Electron Microscopy (TEM) to characterize the early-stage corrosion behavior and thin surface oxide layers. By comparing of oxide films between Al1050 and Al7075 alloys, it is concluded that Al7075 has a relatively thicker surface oxide film than Al1050 but Al1050 has relatively more significant oxygen penetration through grain boundaries. The oxygen penetration through grain boundaries appeared to be influenced by intermetallic particles at the grain boundary. In the case of aluminum alloys, localized corrosion like pitting or intergranular corrosion should be considered as well as uniform corrosion when estimating the atmospheric corrosion rate.

• Wind and Structures
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• v.17 no.1
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• pp.87-105
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• 2013

Modeling an equilibrium atmospheric boundary layer (ABL) in an empty computational domain has routinely been performed with the k-${\varepsilon}$ turbulence model. However, the research objects of structural wind engineering are bluff bodies, and the SST k-${\omega}$ turbulence model is more widely used in the numerical simulation of flow around bluff bodies than the k-${\varepsilon}$ turbulence model. Therefore, to simulate an equilibrium ABL based on the SST k-${\omega}$ turbulence model, the inlet profiles of the mean wind speed U, turbulence kinetic energy k, and specific dissipation rate ${\omega}$ are proposed, and the source terms for the U, k and ${\omega}$ are derived by satisfying their corresponding transport equations. Based on the proposed inlet profiles, numerical comparative studies with and without considering the source terms are carried out in an empty computational domain, and an actual numerical simulation with a trapezoidal hill is further conducted. It shows that when the source terms are considered, the profiles of U, k and ${\omega}$ are all maintained well along the empty computational domain and the accuracy of the actual numerical simulation is greatly improved. The present study could provide a new methodology for modeling the equilibrium ABL problem and for further CFD simulations with practical value.

• Wind and Structures
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• v.35 no.6
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• pp.419-430
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• 2022

In wind-resistant designs, wind velocity is assumed to be a Gaussian process; however, local complex topography may result in strong non-Gaussian wind features. This study investigates the non-Gaussian wind features over complex terrain under atmospheric turbulent boundary layers by the large eddy simulation (LES) model, and the turbulent inlet of LES is generated by the consistent discretizing random flow generation (CDRFG) method. The performance of LES is validated by two different complex terrains in Changsha and Mianyang, China, and the results are compared with wind tunnel tests and onsite measurements, respectively. Furthermore, the non-Gaussian parameters, such as skewness, kurtosis, probability curves, and gust factors, are analyzed in-depth. The results show that the LES method is in good agreement with both mean and turbulent wind fields from wind tunnel tests and onsite measurements. Wind fields in complex terrain mostly exhibit a left-skewed Gaussian process, and it changes from a softening Gaussian process to a hardening Gaussian process as the height increases. A reduction in the gust factors of about 2.0%-15.0% can be found by taking into account the non-Gaussian features, except for a 4.4% increase near the ground in steep terrain. This study can provide a reference for the assessment of extreme wind loads on structures in complex terrain.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2010.04a
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• pp.275-276
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• 2010

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.323-324
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• 2002

최근 동아시아 지역은 높은 인구 밀도와 급격한 에너지 소비 증가로 다량의 대기오염물질들을 방출하고 있다. 특히 우리나라와 인접한 중국은 급속한 공업화로 많은 양의 대기오염물질을 방출하는 것으로 알려지고 있고, 중국의 동부 공업지대에서 발생된 다량의 아황산 가스는 편서풍을 타고 장거리 이동되어 한반도 지역 강우의 산성화를 급속히 심화시킬 것으로 예상된다. 이러한 주변 국가의 오염 영향을 파악하기 위해서는 자체 오염원이 없는 청정지역에서 그 농도를 측정해야 한다. (중략)

• 한국해양학회지
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• v.1 no.1_2
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• pp.1-6
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• 1966

A latitudinal, differential pH distribution is observed in the Northeastern Pacific Ocean with a pH range of 8.15 at high latitude (42 N) to 8.29 at low latitude (23 N). These pH values are generally greater than the calculated equilibrium pH with respect to atmospheric carbon dioxide. If we assume that the calculated equilibrium pH values ae valid, then the surface waters are undersaturated with respect to the atmospheric carbon dioxide during April to June 1966. A high surface pH value of about 8.26 was observed immediately south of the SubarcticBoundary zone near 170 W. This value differs from the equilibration pH by as much as 0.1 unit.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.162-164
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• 2000

The numerical simulation of air movement in a room using CFD (Computational Fluid Dynamics) requires a complicated set of input data, This includes physical data, such as space geometry, characteristics of supply air flow and contaminant source, etc. as well as computational domain. Among the input data, the boundary conditions related to the inlet are particularly crucial in order to achieve accurate computation results, although there are many other parameters which may also affect the results. (omitted)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.301-302
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• 2002

Virtual cyclones have been the subject of aerosol separation studies since they were first developed by Torczynski and Rader (1996). In the virtual cyclone (originally referred to as the anticyclone), the main particle-laden flow follows a wall that curves away from the original flow direction rather than curving into the original direction, as in a cyclone. Although a wall forms the inner boundary of the main flow, its outer boundary is formed by an adjacent flow, often a confined recirculating flow, into which particles are transferred by centrifugal action. (omitted)